It has been estimated that the mangroves surrounding Laguna de Términos, part of this ecoregion, receive at least one third of the population of migrant birds that follow the Mississippi River flyway, another fact that gives special significance to this place as a natural refuge. Mangroves are generally acknowledged to be excellent for soil retention, and this ecoregion behaves in accordance with this biologically important feature. The state of Tabasco, Mexico, within which this mangrove ecoregion lies, holds the greatest share of aquatic vegetation in the country. Associations of aquatic plants are recognized as one of the most representative ecosystems of Mexico. Besides their importance as a unique habitat and the extraordinary display of animal species that inhabits them, mangroves constitute a natural refuge for diverse species of aquatic birds, as they harbor many aquatic organisms on which birds feed (e.g. oysters, crabs, invertebrate larvae, etc.).

Location and General Description

Laguna de Terminos, Campeche, Mexico (Photograph by F. Eccardi/Semarnap)
Usumacinta mangrove ecoregion is located in the state of Tabasco, Mexico. The delta formed by the rivers Usumacinta and Grijalva delineates the mangrove habitat as well as other hydrophyllic communities. Soils are deep, very acidic, and rich in organic matter; this, together with their clay-like nature, makes them among the most productive soils in the country. The climate is warm-humid with abundant rains in summer, and this mangrove ecoregion is one of the wettest, with 1600 millimetres (mm) annually, in the area. Due to its climatic and biologic characteristics, Usumacinta mangroves and the nearby floodlands are considered the most important wetlands of the country. The area is situated in a vast plateau with occasional flood plain formations. The coastal plains form part of the Grijalva-Usumacinta fluvial system, which constitutes Mexico's biggest discharge of freshwater into the ocean. Mangroves carry clay-mud sediments due to the influence of the Usumacinta-Grijalva current. Intrusions of salt water during the dry season allow mangroves to form up to 30 kilometers (km) inland.

The vegetation is established on top of the fluvial plain and on soils with very high organic matter content. Red mangrove (Rhizophora mangle), white mangrove (Laguncularia racemosa), and black mangrove (Avicennia germinans) are the key species in the community, and they are associated with Dalbergia brownii scrubs as well as with other hydrophyllic communities formed by Acoelloraphe wrightii or Sabal mexicana palm trees. As in most mangroves, herbaceous associations are not abundant in these communities because they are intolerant to permanent floods.

Biodiversity Features

It has been estimated that the mangroves surrounding Laguna de Términos, of this ecoregion receive at least 33% of the population of migrant birds that follow the Mississippi route, another fact that gives special importance to this place as a natural refuge. Mangroves are also recognized as good soil retainers, and this ecoregion is not exempt from this biologically important feature. The area contains 374 species of plants, 60 species of fish, 26 amphibians, 85 reptiles, 279 birds, and 134 mammals. Along with the aquatic vegetation that is present in Laguna de Términos, the area contains 1,468 species of aquatic and terrestrial organisms, of which 30 are endemic to Mexico. Moreover, Laguna de Términos holds nearly 90 endangered species. The diverse geomorphological features of Usumacinta mangroves allow the formation of a complex hydrological system of marshes, lagoons, and other water bodies that together share most of the aquatic species of the ecoregion. The area is highly important as a refuge for the manatee (Trichechus manatus), an endangered species.

Current Status

Mangroves have been gradually eliminated in this ecoregion, due to their importance as a source of food and timber for local villagers. It is estimated that only 13.5% of the area encompassed by the mangroves and nearby habitats remain intact. The Usumacinta mangrove ecoregion forms part of the Biosphere Reserve of Pantanos de Centla, which was established in 1992, and were designated as a wetland of international importance under the RAMSAR convention in 1995. Federal protection has begun, and a management plan for the area is currently being undertaken to prevent accelerated habitat loss, and to introduce the idea of sustainable natural resource use in such a rich and biologically diverse ecoregion; one of the most important wetlands in Mexico.

Types and Severity of Threats

Exploitation of local fisheries and of mangrove trees is the major threat to the habitat. This is the primary reason for high numbers of species in danger of extinction, in the state of Tabasco. Habitat fragmentation and destruction are bound to continue, and with them, a major loss of animal species of great importance. The area contains 19 species of threatened animals, as well as 5 that are considered rare species. Moreover, the mangroves and adjacent habitats are home to most of the individuals of storks (Jabiru mycteria) that survive in Mexico, and are the preferred breeding place of the endangered Morelet's crocodile (Crocodylus moreletii).

Long-term threats to the region include overexploitation of resources, continuous industrial pollution of the waters due to human overpopulation, oil extraction, and the possible construction of building a hydroelectric plant that would impact a large part of the aquatic habitat. According to IUCN, the Gulf Coast contains the largest area of wetlands in North America.

Justification of Ecoregion Delineation

Classification and linework for all mangrove ecoregions in Latin America and the Caribbean follow the results of a mangrove ecoregion workshop and subsequent report.

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